Of course it isn't. Replacing a broken window with a new window is almost entirely a waste, perhaps other than making sure the window industry remains marginally more viable.

Much military spending has direct value as surplus goods, scientific advancement, humanitarian support, and patronage for domestic skilled industry. Maybe those benefits, and others, do not justify the expenditures in all cases, but it's far from a "perfect" waste of economic output.

The benefit of a broken window is that you do not have to argue that it has to be replaced. If you have a superior replacement window then this can actually be a net positive but most things just haven't changed that much. It wouldn't surprise me though if war is the only thing that can counteract awful zoning policies.